Compostable v biodegradable
'Compostable' products, e.g. compostable kitchen caddy bags, are made from starch and vegetable oils. They will break down completely in the presence of oxygen and micro-organisms (fungi or bacteria) in a relatively short time frame leaving no physical residues (micro-plastics) or chemical residues harmful to plants or animals.
Look for the looped seedling logo or home compostable logo, the internationally-recognised certification symbols that verify a product's claim of compostability according to the Australian Standards. Certification to European or US standards is also recognised in Australia.
You cannot put plastic bags or bags labelled 'degradable', 'biodegradable' or 'oxo-degradable' in your organics bin or home compost bin. Plastics labelled 'oxo-degradable' are merely plastics with additives to accelerate their breakdown when exposed to UV radiation or heat.
For more information see Soft plastics unwrapped: avoiding the greenwash.